speedometer is way off

[j930]

I installed some new tires last month and they are a bit smaller than what was on there. while driving today I flipped on the GPS on my cell phone to check my speed as I thought I was about to be pulled over(I dod not get pulled over thankfully) and my speedo is off by 10 mph. how does one adjust that?

[j930]

smaller in width but larger in height

[ayebaal]

The same deal with my old 911, a bit wider but less tall than stock. measured the circumference of each and found the shorter size was 10% smaller. So, if you are reading 60 on your speedo you are traveling at about 54, 70=63. 80=72, ect. Seems to work, never been tagged.
930 is different. If it feels like 50 MPH, your probably doing 75.

[JBL930]

The stock speedo on stock tires WAY over reads, mine was around 13% over. 100mph on speedo was actually 87mph on AX22 'and' satnav....

[RichardE]

I agree Jonathon. My standard set up is way too optimistic by about 10mph at 70. Actually, come to think of it my 944 is a bit the same way but not as bad as the 930. Do these things come out of the factrory accurate and just go off over time? Weird.

[voitureltd]

Originally Posted by RichardE

I agree Jonathon. My standard set up is way too optimistic by about 10mph at 70. Actually, come to think of it my 944 is a bit the same way but not as bad as the 930. Do these things come out of the factrory accurate and just go off over time? Weird.

Install a 8:41 R&P instead of the 9:36 and it will be off the other way. Seriously, I think there are company's that can recalibrate ( California speedo and others) or just get a different speedo face plate to adjust the difference. I noticed the speedo being way off on a 1978 930 I have, however on the 87-89 930's I have tested in the past, seemed to be right on. Seems like some same year cars are accurate and some not as I have a stock 77 930 and it is right so the age seems not to be a factor from my experience.

[j930]

but the consensus is that the mileage is ok but the speedometer is off. I have not checked my odometer yet?

[dicklague]

I had North Hollywood Speedometer recalibrate mine.

[schmidlapp]

My 84 euro spec 930 is right on the button.
Have 245 50 16's on the rear on BBS wheels.

[lin7310948]

i put Livorsi gauges in my 930. the speedometer is a GPS. have not had it on the street but it is supposed to be very accurate.

[mooney265]

Neat...

Where's the boost gauge?

[lin7310948]

converting to a modified LS7...most of the info is fed directly to the gauges from the ECU.

[krasuskyp]

Every Porsche I've driven seems to provide 'this' - I call it not MPH but Miles Per Porsche 8-).

Although, I've ran past a number of them speed signs on the roadside in mine and it was dead nuts accurate @ 35-40 - I think the issues start thereafter...